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Heird, J. C., Lennon, A. M., & Bell, R. W. (1981). Effects of early experience on the learning ability of yearling horses. J. Anim Sci., 53(5), 1204–1209.
Abstract: Twenty-four yearling Quarter Horse fillies were divided into three groups (I) very limited handling, (II) intermediate handling and (III) extensive handling. At about 14 months of age, each horse was preconditioned for 2 weeks and then run in a simple place-learning T-maze test in which it had to locate its feed. Thirty trials were run daily for 20 days, with the location of the feed changed each day. To retire from the maze, a horse had to meet the criterion: 11 correct responses in 12 tries, with the last eight being consecutive. Horses in Group II required the fewest trials to reach criterion. These horses also learned more and had the highest percentage of correct responses (P less than .05). Mean trainability tended to predict learning ability; however, trainability and trials to criterion were not significantly correlated. Mean emotionality scores indicated a tendency for horses in the intermediately handled group to be less emotional than those in Group I or III. Results indicated that horses with an intermediate amount of handling scored higher on an intermediate test of learning. All handled horses scored higher on learning tests than those not handled.
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Houpt, K. A., Parsons, M. S., & Hintz, H. F. (1982). Learning ability of orphan foals, of normal foals and of their mothers. J. Anim Sci., 55(5), 1027–1032.
Abstract: The maze learning ability of six pony foals that had been weaned at birth was compared to that of six foals reared normally. The foals' learning ability was also compared to their mothers' learning ability at the same task; the correct turn in a single choice point maze. The maze learning test was conducted when the foals were 6 to 8 mo old and after the mothered foals had been weaned. There was no significant difference between the ability of orphaned (weaned at birth) and mothered foals in their ability to learn to turn left (6 +/- .7 and 5.1 +/- .1 trials, respectively) or to learn the reversal, to turn right (6.7 +/- .6 and 6.2 +/- .6 trials, respectively). The orphan foals spent significantly more time in the maze in their first exposure to it than the mothered foals (184 +/- 42 vs 55 +/- 15 s. Mann Whitney U = 7, P less than .05). The mothers of the foals (n = 11) learned to turn left as rapidly as the foals (5.9 +/- .7 trials), but they were slower to learn to turn right (9.8 +/- 1.4 vs 6.4 +/- .4 trials, Mann Whitney U = 33, P less than .05), indicating that the younger horses learned more rapidly. There was no correlation between the trials to criteria of the mare and those of her foal, but there was a significant negative correlation between rank in trials to criteria and age (r = -65, P less than .05) when data from the mare and foal trials were combined. The dominance hierarchy of the mares was determined using a paired feeding test in which two horses competed for one bucket of feed. Although there was no correlation between rank in the hierarchy and maze learning ability, there was a correlation between body weight and rank in the hierarchy (r = .7, P less than .05). This may indicate either that heavier horses are likely to be dominant or that horses high in dominance gain more weight. Maternal deprivation did not appear to seriously retard learning of a simple maze by foals, although the orphans moved more slowly initially. The lack of maternal influence on learning is also reflected in the lack of correlation between the mare's learning ability and that of her foal. Young horses appear to learn more rapidly than older horses.
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Turner, J. W. J., & Kirkpatrick, J. F. (1982). Androgens, behaviour and fertility control in feral stallions. J Reprod Fertil Suppl, 32, 79–87.
Abstract: This field study of feral stallions in Montana and Idaho examines and correlates the seasonal pattern of plasma androgens and specific sociosexual behaviour and reports the effect of a long-acting androgenic steroid on this behaviour and on fertility. Plasma testosterone was measured by competitive protein binding assay in samples obtained by jugular venepuncture from captured animals. In samples taken from 34 sexually mature stallions in 6 different months during the year, a definite seasonal pattern in testosterone was present, with a peak in May (3.04 +/- 0.63 ng/ml) and a nadir in December (1.55 +/- 0.34 ng/ml). Values were less than 2.0 ng/ml in non-breeding months and greater than 2.4 ng/ml in breeding months. Behavioural endpoints measured were (1) stallion scent marking in response to elimination by mares (elimination marking), (2) mounting and (3) copulation. The frequencies of each of these endpoints followed closely the seasonal pattern seen for plasma androgens. In the fertility study microcapsulated testosterone propionate (microTP) was administered i.m. to 10 harem stud stallions 3 months before the 1980 breeding season. In these stallions and in 10 control harem studs, the above behavioural endpoints were examined in the 1980 and 1981 breeding seasons, and foal counts were made in 1981. There were no direct inhibitory or stimulatory effects of microTP treatment on any of the behavioural endpoints in either year. In 1981 foals were produced in 87.5% of the control bands and 28.4% of the microTP-treated bands. These results indicate that microencapsulated testosterone propionate can provide effective fertility control in feral horses without causing significant alterations in sociosexual behaviour.
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Tobin, T., & Combie, J. D. (1982). Performance testing in horses: a review of the role of simple behavioral models in the design of performance experiments. J Vet Pharmacol Ther, 5(2), 105–118.
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Klingel, H. (1982). Social organization of feral horses. J Reprod Fertil Suppl, 32, 89–95.
Abstract: The basic social unit in feral horses is the family group consisting of one stallion, one to a few unrelated mares and their foals. Surplus stallions associate in bachelor groups. Stallions are instrumental in bringing mares together in a unit which then persists even without a stallion. The similarity of social organization in populations living in a variety of different habitats indicates that feral horses have reverted to the habits of their wild ancestors, and that domestication has had no influence on this basic behavioural feature.
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Stahl, F., & Dorner, G. (1982). Responses of salivary cortisol levels to stress-situations. Endokrinologie, 80(2), 158–162.
Abstract: A procedure is described for determining salivary cortisol levels by a competitive protein-binding assay using horse transcortin. The collection of saliva was performed by means of filter paper-strips. Filter paper samples are more than 5 days stable after air-drying. In this form, the samples could be stored without refrigerator or deep-freezer and, if necessary, sent by post to the laboratory without any special precaution. Stressful situation of either painful or anxious origin were associated with an adequate increase of salivary cortisol levels. The increases were 157 to 230% of the initial or normal values dependent on the kind of stress. The mean values in 4 cases of Cushing's syndrome were 380% and 1 hour after 25 I.U. ACTH 690% higher than those in normal persons. In normal persons, a well-defined circadian rhythm has been observed.
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Lindsay, F. E., & Burton, F. L. (1983). Observational study of “urine testing” in the horse and donkey stallion. Equine Vet J, 15(4), 330–336.
Abstract: Although “urine testing” is said to enable the male equid to assess the sexual status of the mare, there are no reports in the literature of any detailed study of this behavioural response of the stallion. Behavioural response to conspecific urine was studied in two horse stallions and one donkey stallion. The relevant nasopalatine anatomy is described. Events observed during urine testing included head, neck, lip, jaw, tongue movements, penile changes and nasal secretion. Nasal endoscopy indicated that the source of part of the nasal secretion was the secretory glands of the vomeronasal organ complex. The significance and probable function of these events in urine testing is discussed.
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Henneke, D. R., Potter, G. D., Kreider, J. L., & Yeates, B. F. (1983). Relationship between condition score, physical measurements and body fat percentage in mares. Equine Vet J, 15(4), 371–372.
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Wolfe, J. M. (1983). Hidden visual processes. Sci Am, 248(2), 94–103.
Abstract: Isoluminant stimulus is an image whose edges are defined only by a change in color, not by change in brightness. The stimulus here is imperfect: the blue parts and the green parts of the image are only as nearly equal in brightness as they can be on the printed page. Moreover, the change in brightness beyond the edge of the page is apparent, and so is the fact that the reader is holding the magazine at reading distance. When such cues are removed under laboratory conditions, subjects faced with an isoluminant stimulus prove unable to bring its edges into focus. This deficiency contributes to making a familiar face hard to recognize. The experiment indicates that the brain process underlying visual accommodation (the focusing of the eyes) cannot “see” color; it is a hidden process distinct from the processes that lead to perception. The image shows Groucho Marx as he appeared in the motion picture Horse Feathers.
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Berger, J. (1983). Induced abortion and social factors in wild horses. Nature, 303(5912), 59–61.
Abstract: Much evidence now suggests that the postnatal killing of young in primates and carnivores, and induced abortions in some rodents, are evolved traits exerting strong selective pressures on adult male and female behaviour. Among ungulates it is perplexing that either no species have developed convergent tactics or that these behaviours are not reported, especially as ungulates have social systems similar to those of members of the above groups. Only in captive horses (Equus caballus) has infant killing been reported. It has been estimated that 40,000 wild horses live in remote areas of the Great Basin Desert of North America (US Department of Interior (Bureau of Land Management), unpublished report), where they occur in harems (females and young) defended by males. Here I present evidence that, rather than killing infants directly, invading males induce abortions in females unprotected by their resident stallions and these females are then inseminated by the new males.
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